This invention relates to a method for correcting unevenness of phosphor luminance in a color fiber optic cathode-ray tube.
FIGS. 1 and 2A and 2B show one example of a color fiber optic tube (called FOT hereinafter) 1 which is provided with a substantially rectangular fiber optic plate (called FOP hereinafter) 2 at the front end thereof. A single electron gun 3 is connected to the rear end of the FOT 1 for generating an electron beam 4 and a plurality of fluorescent screens 5 each comprising an illuminant color material are laminated on the inner surface, facing the electron gun 3, of the FOP 2. On the fluorescent screens 5, for example, as shown in FIGS. 2A and 2B, phosphors 5R, 5G, and 5B are applied in a band-like form, the phosphors 5R, 5G and 5B possessing fluorescent characteristics of a red color (R), a green color (G) and a blue color (B), respectively. Information regarding the respective colors of the phosphors 5R, 5G and 5B is sensed through the FOP 2 by a color photo-sensitive material 6 which is used for recording the information and which closely adheres to the FOP 2 and moves upward, for example.
A driving method for the FOT 1 mentioned above will be described hereunder in connection with a color picture signal PS for a raster scan type display. An electron beam 4 from the electron gun 3 is scanned so as to synchronize the red, green and blue phosphors 5R, 5G and 5B formed on the rear surface of the FOP 2 with deflection signals of input picture signals, and when the electron beam 4 passes the fluorescent screens 5, picture signals SR, SG and SB respectively corresponding to the phosphors 5R, 5G and 5B are selected and luminance modulation is carried out with a selected picture signal PS. More specifically, with reference to FIG. 3, during the time interval t0-t1 when the electron beam 4 scans the red phosphor 5R, the picture signal SR representing the red color component is selected and modulated into an electric current of the electron beam so as to illuminate the red phosphor 5R and thereby sensitize the color photo-sensitive material 6. In a like manner, during the time intervals t1-t2 and t2-t3 when the electron beam 4 scans the green and blue phosphors 5G and 5B, the picture signals SG and SB respectively representing the green and blue color components are selected and modulated. Accordingly, the picture signals SR, SG and SB are sequentially recorded timewise on the photo-sensitive material 6, the picture signal PS represents the picture signal SR, SG or SB which is selectively composed in synchronism with the scanning position of the electron beam 4 and the luminance modulation in the FOT 1 can be realized by the picture signal PS.
The principle for carrying out color recording operation using the FOT 1 of the type mentioned above will be described hereunder in conjunction with FIGS. 4 through 6.
FIG. 4 shows a still color picture 10A displayed on a color cathode ray tube (CRT) of a raster scan type, and a rectangular part 10B of the color picture 10A is subjected to the sampling operation in accordance with the raster scanning method and displayed on the FOP 2 of the FOT 1 as shown in FIG. 5. The picture displayed on the FOP 2 is color-separated, in a band-shape, into three colors of red, green and blue, and the luminance thereof is modulated with picture signals SR, SG and SB of the separated colors corresponding to the phosphors 5R, 5G and 5B, respectively. The still color picture 10A is sequentially displayed by a portion of the part 10B thereof while shifting the necessary picture elements in a predetermined direction 11 on the red, green and blue phosphors 5R, 5G and 5B formed in a band-shape on the FOP 2 as shown in an electric light display board. In this manner, the picture which is displayed on the FOP 2 of the FOT 1 and is moved thereon is sensed by the color photo-sensitive material 6 which adheres closely to the front surface of the FOP 2 and is moved at the same speed as that of the displayed picture in the predetermined direction 11. Accordingly, in the case where the electron beam 4 crosses the red phosphor 5R to carry out the luminance modulation, information regarding only the red color in the inputted picture signal is recorded as a latent image by the color photo-sensitive material 6. In the same manner, information regarding the green and blue colors are color-separated and exposed, in a band-shape, by the color photo-sensitive material 6. Thus, one sheet of the completed color latent image picture is recorded by the color photo-sensitive material 6 by moving the sensitive material in synchronism with the display picture and recording them in an overlapping manner.
Since the FOT 1 and the photo-sensitive material 6 of the type described above have uneven sensitivity characteristics with respect to the respective color and output picture element positions, a high quality picture output cannot be obtained when the beam irradiates the illuminating positions of the respective phosphors under the same operating conditions.